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Controlling NOx emissions from vehicles is a key aspect of meeting new regulations for cars and trucks across the world. Selective Catalytic Reduction (SCR) with urea-water injection is a NOx reduction option that many engine manufacturers are adopting. The performance of urea-water spray evaporation and mixing upstream of an SCR catalyst is critical in obtaining reliable NOx reduction. Achieving this goal requires good ammonia and NOx distribution upstream of the SCR catalyst brick. Computational Fluid Dynamic (CFD) simulations of urea-water injection systems have become an important development and diagnostic tool for designers. An effective modeling approach for urea/SCR must include spray distribution, evaporation, urea kinetics, wall interactions and heat transfer. Designers are also interested in reducing mesh generation time to expedite geometry design changes and optimizing mesh size for accuracy and solution time.